Team to tackle mite-vectored disease management

By KAY LEDBETTER AgriLife Today

Published 9:37 am, Wednesday, September 4, 2013

Wheat streak mosaic - and the need to develop an integrated management program for all mite-vectored diseases of wheat - will be the focus of a new grant received by Dr. Charlie Rush, Texas A&M AgriLife Research plant pathologist in Amarillo.

The grant, provided through the National Institute of Food and Agriculture Southern Region Integrated Pest Management program, will help researchers update 1950s and 1960s technology and methods currently used to control mites and diseases they transmit, Rush said.

The primary methods of control in place since the wheat curl mite was discovered have been to plant wheat later and control volunteer wheat in the off-season, he said.

“Both of those are still relevant, but a cattleman planting wheat for grazing can’t wait to plant, and not everyone can control the volunteer sources around them, such as Conservation Reserve Program grass fields and other places that serve as an over-summer host for the mites,” Rush said.

The need exists to come up with some new ideas, as there are no new miticides for control of the wheat curl mite, he said.

“And even if there were, growers don’t know when to control,” Rush said. “Through our grant, we will screen new chemistries coming on the market and evaluate them for efficacy.

“But we also will be going to work to understand mite ecology and epidemiology - where do they build up, why and when do they move - so we can determine how to best protect your crop.”

Rush said ultimately the team would like to develop an economic threshold for the mite/virus.

The two-year grant started Sunday with two components: $140,000 for research and another $35,000 for Extension efforts.

The team will include Rush; Dr. Ed Bynum, Texas A&M AgriLife Extension Service entomologist in Amarillo; and graduate and undergraduate students, all doing the research. Bryan McCormick, Kansas State University, and Bob Hunger and Tom Royer, both with Oklahoma State University, will be working on the Extension efforts.

“The goal is never to completely eliminate but rather to control at an economic level,” Rush said. “This has not been done for mite-vectored diseases.”

He said the grant was developed to answer questions for growers who would say they knew they had wheat streak virus in their fields and knew it would spread, but didn’t know if they should continue to apply water and fertilizer.

“The answer would depend on when we got the call,” Rush said. “We realized we needed a better understanding of how disease presence at a particular time would affect yield.”

With precision agriculture efforts that are already in place, producers are able to treat portions of the field according to need, he said. What is missing is how to determine need.

Rush and his AgriLife Research plant pathology team have been working on trials that were examining disease development, whether it was wheat streak mosaic or triticum mosaic. Starting in the fall of 2012, wheat plots were checked every week and hot spots were monitored to see how the natural gradient of mites moved.

“We made disease ratings with a hand-held hyperspectral ground spectrometer and measured/monitored the disease development and then correlated that to yield results,” he said.

“We were able to get some extremely encouraging results.”

They were able to see where mechanically inoculated plants infected at specific times other than those with natural infestations differed in the progress of the gradient spread.

“We found that if you have infestations of mites at a particular time, early in the season with high temperatures, you will have disease development. If it is too cold, the virus appears to not survive in the plants.

“We also found if a field gets the disease after mid-April, and it wasn’t there before, it looks like that would be late enough for the farmer to continue to apply inputs such as water and fertilizer and maintain yield,” Rush said.

He said the goal is, after a year or two, “we will be able to tell producers more specifics to help them know when and where to apply inputs. This way we can provide farmers with a tool to manage their fields in a site-specific manner, and not waste money on disease management.”

Rush’s team also will work to plug in their information with the iWheat program that is being developed by another group of researchers to make a mobile scouting and disease forecasting risk assessment model.